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updated kettle souring to include info about haze from boiling low pH wort.
In order to address the challenges of creating a sealed environment in a commercial boil kettle, which is often left open to the environment through the boil stack, some commercial brewers find it beneficial to rack the wort from the boil kettle to a mashtun, brite tank, fermenter (often dedicated), or another vessel that seals and purges well to sour in. The mashtun or other vessel is first cleaned, sanitized, and often purged with CO2. Once the wort is in the vessel, and at the correct temperature for the given culture of ''Lactobacillus'', the ''Lactobacillus'' is pitched into the vessel and the vessel is sealed off. If the vessel is sealed and air tight temperature shifts from cooling won't suck air into the vessel and a potentially more sanitary souring fermentation will occur. Using a fermenter or brite tank (if there are multiple) has the advantage of not occupying a bottleneck vessel such as the mashtun or boil kettle, but has more risk if the fermenter is not dedicated to kettle souring. Dedicating removable soft parts like gaskets and hoses will minimize the risk of infection originating from the fermenter or brite tank if it is not dedicated to souring <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1778027798892093/ Various professional brewers. Milk The Funk Facebook post about souring in a mashtun, brite tank, or other vessel for commercial brewers. 08/02/2017.]</ref>.
Once the level of acidity is reached (this can be tested with a reliable [[PH_Meter|pH meter]], or in the case of using a pure culture can safely be taste tested), the wort is brought to a boil. The wort may be boiled normally in the case of any style of beer that requires a longer boiling process, or it may be boiled for no more than a minute or two in the case of making a [[Berliner Weissbier]]. Technically speaking, the wort doesn't need to be boiled at all (this is called [http://www.garshol.priv.no/blog/331.html Raw Ale]). Heat pasteurization at 140°F (60°C) for 15 minutes should kill the ''Lactobacillus'' culture being used to sour the wort <ref name="pasteurization" />. Note that boiling a soured wort that has a pH lower than 5.0 will decrease the amount of protein coagulation, potentially resulting in a hazier beer or more sediment in the fermenter <ref>[http://beerandwinejournal.com/proper-boil-ph/ Chris Colby. "Easy way to Hit The Proper Boil pH". Beer and Wine Journal blog. 07/01/2013. Retrieved 03/02/2018.]</ref>. Haze and sediment can be avoided by choosing to boil long enough to hit a hot break ''before'' souring the wort (see [https://www.facebook.com/groups/MilkTheFunk/permalink/2008265249201679/?comment_id=2008553569172847&reply_comment_id=2008577055837165&comment_tracking=%7B%22tn%22%3A%22R%22%7D example MTF post from Chris Prechel]). Raw ales are also fairly hazy in nature due to the lack of hot break from boiling.
Deciding whether or not to boil the wort can also depend on whether or not there was a considerable amount of alcohol produced as commonly happens when the wort is contaminated with yeast. Pure cultures of ''Lactobacillus'' do not show typical signs of fermentation that we are used to seeing with yeast fermentations, such as forming a krausen, producing a lot of CO2, or fermenting wort more than ~1.005 gravity points (see [[100% Lactobacillus Fermentation]]). See [[Wort_Souring#Dealing_With_Yeast_Contamination|Dealing With Yeast Contamination]] below.